GPS and InSAR constraints on vertical tectonic motion improve the estimate of slip rate of the San Andreas Fault in southern California

The San Andreas fault (SAF) is the fastest slipping member of a complex plate boundary system that poses a
looming earthquake hazard to millions of people in southern California. Seismic hazard analysis products rely on
accurate estimates of fault slip rate in order to best forecast the shaking from future damaging earthquakes. Data
from geodetic GPS networks such as the EarthScope Plate Boundary Observatory, SCIGN, and other municipal
networks place strong constraints on faults slip rates. However, models based geodetic measurements in the
eastern Transverse Ranges suffer from uncertainties in fault dip, slip history, and viscoelastic Earth structure. Part
of the problem is that data are commonly limited to horizontal interseismic rates of motion at GPS stations.